1. Field of Invention
This invention relates to machines for rollforming sheet metal, and has particular application to rolling edge profiles along one rectilinear edge of a sheet metal duct element or other workpiece, the profile having at least one variable dimension which must be accommodated by shift of some of the forming rolls relative to the others.
2. Description of the Related Art
A typical utilization of rollforming equipment is in the forming of edge flanges on substantially rectangular pieces of sheet metal, such as end edge flanges on sections of heating or cooling ducts.
Known profiles for the end edges of such duct sections include the type of outstanding flange with a succession of bends sized to receive and engage cornerpieces, such as the snap-in flanges shown in U.S. Pat. No. 3,886,779. In this specification, that flange profile is used to illustrate how, utilizing a rollformer machine of the present invention, the end flanges may be formed to variable chosen depths without removing and re-spacing the roll sets.
Specifications applicable to a single duct installation may permit or require the larger cross-section ducts to have substantially deeper flanges than ducts of smaller cross-section. To make a deeper integral flange, the bend line at the base of the flange must be spaced farther from the edge than the bend line at the top of the flange. To change such spacing, as from shallower to deeper, has heretofore required that all the rolls, mounted on those stations of the machine which form the variable part of the flange profile, be removed from the ends of the spindles to which they are secured and other rolls substituted, or, in some instances, re-positioning the original rolls by insertion or removal of spacers.
The problem of varying flange conformation along one edge of a sheet is quite different than that met by familiar "dual head" machines, which simultaneously form opposite edges of a metal workpiece.
Conventional "single head" multi-station progressive roll formers, used for forming integral flanges along one edge of a sheet metal workpiece, are comprised of two principal housing assemblies:
(1) a gear train housing assembly, made up of a lower power train whose alternate gears are mounted on lower roll-driving spindles, and an upper frame portion mounted thereon with provision for yielding under spring pressure, the upper frame portion having meshing gears mounted on upper roll-driving spindles which extend therefrom; and
(2) a forming roll housing assembly mounted adjacent to and at a fixed spacing from the gear train housing assembly, made up of a lower frame roll-housing portion and upper frame roll-housing portion similarly mounted yieldably thereon, through which housing assembly on the roll-driving spindles extend with forming rolls mounted on their outboard side.
Where complex bends are to be formed parallel to a sheet metal edge, and inboard of a first set of bends, it is known practice to form in the metal a simple tracking groove (or ridge) at an early roll-form stage, and to accommodate this in the rolls of all subsequent forming stations to assure parallel lines of bend within close tolerances.